The present invention relates to an assembly to drive conveyor rollers. More specifically, the present invention is concerned with such a coupling assembly provided with a magnetic clutch device.
Conveyor systems provided with power driven rollers are well known in the art. They are generally used to move objects to and from various locations following a predetermined path.
Means for engaging and disengaging coupling assemblies from conveyor rollers are also well known in the art since it is often necessary to stop the conveyor rollers when the accumulation of the objects moved by the conveyor occurs to prevent the objects, the conveyor driving mechanism and/or the conveyor rollers from being damaged should the conveyor be continuously powered under these conditions.
One method used for stopping powered conveyor rollers is to provide slip clutches thereon for the purpose of achieving slippage between driving and driven components when the torque required to move the objects reaches a predetermined level. Of course, the rotation of the driven portion generally resumes once there is no more immobilization.
Example of such slippage clutch arrangements includes the use of a series of friction disks pressed axially together by force applied by spring or magnetic forces.
An example of a magnetic type of coupling assembly for driving a conveyor roller is described in U.S. Pat. No. 4,469,220 issued Sep. 4, 1984, naming Lynn T. Becker et al. as inventors and entitled xe2x80x9cMagnetic coupling assembly for accumulating power roll conveyorxe2x80x9d. The system described by Becker automatically disengages the conveyor roller from the coupling assembly when an accumulation of the objects being moved by the conveyor occurs. Becker""s system has many drawbacks. For example, since the coupling assembly is in line with the conveyor roller, maintenance is more difficult. Furthermore, the adjustment must be done manually on each roller and, since the adjustment is done via a continuous thread, it may prove difficult to adjust the same air gap on each roller.
Another example of a driving conveyor roller is described in U.S. Pat. No. 4,063,636 issued Dec. 20, 1977, naming vom Stein as the inventor and entitled: xe2x80x9cDisconnectable driving roller for roller conveyorsxe2x80x9d. This disconnectable driving roller has individual driving roller groups isolated from a common conveyor drive. This is an improvement over Becker""s system since more than one conveyor roller may be disconnected simultaneously. This system is however relatively mechanically complex and therefore more costly to manufacture and to maintain.
Another aspect also known for conveyor systems are means for detecting movements, gaps or presence of conveyed objects on the conveyor. Such existing devices include, photosensor, induction sensor and optical sensor, for example. Any detected anomaly by these sensors is supplied to the conveyor system for further action.
It is therefore only possible to detect gaps between objects on a conveyor system with such a sensor. However, it appears to be difficult, when no gap is detected, to determine if the objects are so close together that there is no gap while the conveyor is moving or if the conveyor is stopped.
More specifically, in accordance with the present invention, there is provided a magnetic coupling assembly to selectively couple a drive element of a longitudinal conveyor to at least one conveyor roller; the coupling assembly comprising:
a driving portion configured and sized to be mounted to the conveyor; the driving portion being so configured as to be rotatably driven about a rotation axis by the drive element of the conveyor;
a driven portion so linked to the driving portion as to rotate about the rotation axis; the driven portion including an external surface configured and sized to be brought in contact with at least one conveyor roller;
an axially movable element mounted to one of the driving and driven portions; the axially movable element being provided with a first friction surface; the other of the driving and driven portions including a second friction surface facing the first friction surface;
wherein one of the axially movable element and the other of the driving and driven portions is provided with a magnetic field generating element; the other of the axially movable element and the other of the driving and driven portions being provided with an element made of magnetic material;
whereby the first and second friction surfaces are brought in contact by a magnetic force present between the magnetic field generating element and the element made of magnetic material.
According to another aspect of the present invention, there is provided a conveyor section configured to be part of a conveyor providing with a drive element, the conveyor section comprising:
first and second laterally spaced apart longitudinal side rails;
a plurality of conveyor rollers mounted to the first and second side rails;
at least two coupling assemblies mounted to the first side rail; each coupling assembly including:
a driving portion configured and sized to be mounted to the first side rail; the driving portion being so configured as to be rotatably driven about a rotation axis by the drive element of the conveyor;
a driven portion so linked to the driving portion as to rotate about the rotation axis; the driven portion including an external surface configured and sized to be brought in contact with at least one conveyor roller;
an axially movable element mounted to one of the driving and driven portions; the axially movable element being provided with a first friction surface; the other of the driving and driven portions including a second friction surface facing the first friction surface;
a longitudinal element so mounted to the first side rail as to reciprocate between an engaged position where it is close to the coupling assemblies and a disengaged position where it is distant from the coupling assemblies;
wherein one of the axially movable element and the longitudinal element is provided with a magnetic field generating element and the other of the axially movable element and the longitudinal element is provided with an element made of magnetic material;
whereby the first and second friction surfaces are brought in contact by a magnetic force present between the magnetic field generating element and the element made of magnetic material.
According to a third aspect of the present invention, there is provided a detecting assembly for a conveyor provided with at least one coupling assembly mounted to a side rail and coupling a drive assembly to rollers of the conveyor; the coupling assemblies including a driving portion mounted to a side rail and a driven portion linked to the driving portion; the detecting assembly comprising:
a detectable element mounted to the driven portion;
a sensor so mounted to the conveyor as to detect the movement of the detectable element to determine the rotation of the driven portion and of the rollers.
Other objects, advantages and features of the present invention will become more apparent upon reading of the following non restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings.